Method of mineral tanning



Patented Dec. 19, 1933 PATENT OFFICE METHOD OF MINERAL TANNING Ian 0. Somerville, Fox Chase, Pa., assignor to Rohm & Haas Company, Inc., Philadelphia,

No Drawing. Application January 20, 1933 Serial No. 652,687

10 Claims.

This invention relates to a new method of mineral tanning.

The earliest mineral salt to be used in the conversion of raw skin into leather was alum, and it this tannage is still used to some extent in the manufacture of white leather. It has the disadvantage that the leather is not stable against prolonged washing nor resistant to hot water. An improvementv in both these respects was effected in the introduction of salts of chromium as tanning agents, and this process is universally used where a stable tannage resistant to hot water is desired. Leather made in this way, however, has a greenish blue color, and it is extremely difiicult to modify this tannage to give white leather. Consequently other mineral salts have been tried in an endeavor to give a stable tannage which would have a white color, and patents have been taken out covering the use of salts of magnesium, silicon, titanium, tin and others.

I have now discovered that the salts of zirconium can be used to produce stable white leather resistant to prolonged washing and to hot water, which has a different character to that produced with other mineral salts such as magnesium or titanium.

Whereas it is diflicult to secure tannage with titanium salts, zirconium salts, such as the sul phate, of considerable range of basicity have now been found to combine readily with pickled skin, even in quite acid condition. The method of procedure is illustrated in the examples set out below. In general it may be said that water soluble salts of zirconium can be utilized, such as the chloride, nitrate, or sulphate, though the sulphate appears to be the most suitable for development on a practical scale. The whitest leather results from the use of a solution of the to pure sulphate, but good leather may besecured even if a technical product is utilized. This may contain traces of iron or titanium, but these do not produce an appreciable effect on the quality of the leather. The range of basicity allowable 5 at the time of application to the skin is considerable, but I prefer to apply the zirconium salt in stronglyacid condition, and neutralize all excess of acid by'washing or addition of mild alkalies.

A still milder neutralizing action can be secured by adding a small amount of an organic acid such as gluconic acid to the solution before commencing the addition of the alkali.

As a further development of this invention I have found it possible to utilize the salts of zirconium in conjunction with other standard types of tannage. For example it is possible to effect a combination tannage with salts of zirconium and chromium. The zirconium salts may be applied first, and followed by chromium, or a chrome tannage may be modified by subsequent treatment with zirconium salts. A similar combina-- tion tannage can be carried out with aluminum and zirconium salts. Further it is possible to improve the character of formaldehyde-tanned leather by application of zirconium salts after $5 the formaldehyde has been taken up. Another important method of use of zirconium salts in tanning is to apply them in conjunction with suitable synthetic tanning agents. In this way white leather with different characteristics may 7 be obtained dependent on the nature of the synthetic tanning agent selected. It is also possible to use zirconium salts in conjunction with the vetgetable tannins.

The following examples illustrate the different 35 types of tannage in which zirconium salts may be utilized, but it is understood that the invention is in no way confined to these examples:

1. A solution of zirconium sulphate containing 20% ZlOz was usedto tan pickled sheepskin as follows: 100 lbs, pickled sheepskin showing pI-I less than 2 was drummed in 300 lbs. of 5% solution of sodium chloride, and 35 lbs. of tanning solution added in one feed. After drumming for 6 hours the skins felt tanned. The liquor was drained, and the skins washed with water until a pH of 4 /2 was reached, then dried out. By rewetting and staking good white leather was obtained.

2.- A solution of zirconium chloride was prepared by dissolving basic zirconium carbonate in an amount of concentrated hydrochloric acid calculated to give ZIOClz, and diluting to a solution containing theequivalent of 20% ZrOz.

100 lbs. pickled sheepskin showing pH 2 /4 was drummed in 250 lbs. 10% solution of sodium chloride and 25 lbs. of tanning solution added in 3 feeds at half hour intervals. Drummed 2 hours, lay overnight in liquor, then a solution of sodium bicarbonate added in successive portions 100 till a pH of over 4 was reached. Skins were washed well, and dried out.

3. A solution of zirconium nitrate was prepared in a manner similar to the chloride by dissolving basic zirconium carbonate in nitric acid and di- 105 luting to a solution containing the equivalent of 20% ZrOz.

100 lbs. pickled sheepskin showing pH 2 was drummed in 300 lbs. 10% solution of sodium chloride and 30 lbs. of tanning solution added in 5 1 10 feeds at /2 hour intervals. Drummed four hours after the last addition. The liquor was drained, and the skins drummed in 300 lbs. of 5% salt solution to which was added 3 lbs. gluconic acid, then a solution of borax in successive feeds until a pH of 5 was reached. The skin's'were washed, then fatliquored with 5 lbs. sulphonated cocoanut oil and dried out.

4. (a) 100 lbs. of calfskins were taken in the pickled condition and given 6 lbs. of a one third basic chromium sulphate, then 5 lbs. of the tanning solution described in Example 1. After drumming for 5 hours, the skins were neutralized to pH 4, washed well, fatliquored with 5 lbs. sulphonated neats-foot oil, and dried out.

(1)) 100 lbs. of calfskins were taken in the pickled condition and given 10 lbs. of the tanni solution described in Example 1. After drumming 3 hours, sodium carbonate was added until a pH of 3% was reached, then 3 lbs. of acne third basic chromium sulphate added. After drumming 2 hours sodium carbonate was added very slowly until a pH of 4 was reached, and the skins allowed to lie in the liquor overnight. In the morning they were processed as is customary for chrome tanned calfskin and gave good leather of bluish white color.

5. 100 lbs. of pickled sheepskins were drummed in 300 lbs. of 5% solution of sodium chloride, and given 20 lbs. of the tanning solution described in Example 1. Drummed for 4 hours, drained, and in a fresh liquor of 5% salt given 8 lbs. of aluminum sulphate. Drummed 4 hours, allowed to lie in liquor overnight, and next day sodium bicarbonate added in successive feeds until a pH of 4 was reached. Skins were rinsed, fatliquored with a mixture of 4 lbs. neats-foot oil and 3 lbs. Ivory soap, and dried out.

6. 100 lbs. of bated kidskins were given a light pickle with sulfuric acid and salt. then treated with 10 lbs. of a 37% solution of formaldehyde. Drummed for 3 hours, then neutralized to a pH of 7 and allowed to lie in the liquor overnight. Next day given 5 lbs. of the tanning solution described in Example 2, drummed for 3 hours, then washed until a pH of 4% was reached, fatliquored as in Example 5, and dried out.

'5. 100 lbs. of pickled calfskins showing pH of 2 were drummed with 300 lbs. of a 5% solution of sodium chloride and 20 lbs. of the tanning solution described in Example 1 added. Drummed for 4 hours, then neutralized with sodium bicarbonate to a pH of 3 Liquor was drained and the skins rinsed lightly, and divided into 4 parts. In fresh salt solution 5 lbs. of solutions of various synthetic tanning agents were added:

(a) Consisting of the product of condensation of phenol sulphonic acid and formaldehyde;

(b) Consisting of the product of sulphonation of the viscous resinous liquid produced by condensation of phenol with acetaldehyde;

(0) Consisting of the product of condensation of naphthalene sulphonic acid and formaldehyde;

(d) Consisting of the product of sulphonation of 4.4-dihydroxydiphenyldimethylmethane.

After drumming with the synthetic tanning agent for 3 hours, the skins were washed well, fatliquored, and dried out.

8. 100 lbs. of side leather which had been tanned by slow addition of a blend of quebracho and chestnut extracts was treated towards the conclusion of tannage with 5 lbs. of the tanning solution described in Example 1. After washing well, the skins were fatliquored, and dried out in the usual way.

The above examples illustrate several embodiments of the invention, but wide deviation is possible without departing from the spirit of the invention, the scope of which is limited only by the following claims:

What I claim is:

1. A process of tanning consisting in the application of water soluble salts of zirconium to hide or skin.

2. A process of tanning consisting in the application of Water soluble salts of zirconium to pickled skin, with subsequent washing to remove free acid.

3. A process of tanning consisting in the application of water soluble salts of zirconium to pickled skin, with subsequent addition of a mild alkali to neutralize free acid.

4. A process of tanning consisting in the application of a solution of zirconium sulphate to pickled skin, with subsequent neutralization of free acid.

5. A process of tanning consisting in the application of a solution of zirconyl chloride to pickled skin with subsequent neutralization of free acid.

6. A process of tanning consisting in the application to hide or skin of water soluble salts of zirconium in conjunction with salts of chromium.

7. A process of tanning consisting in the application to hide or-skin of water soluble salts of zirconium in conjunction with salts of aluminum.

8. A process of tanning consisting in the application to hide or skin partially tanned with formaldehyde, of water soluble salts of zirconium.

9. A process of tanning consisting in the application to hide or skin of water soluble salts of zirconium in conjunction with synethetic tanning agents.

10. A process of tanning consisting in the application to hide or skin partially tanned with vegetable tanning materials, of water soluble salts of zirconium.

IAN C. SOMERVILLE. 

